Jet engine nacelle with dampers for half-shells

ABSTRACT

The present invention relates to a jet engine nacelle ( 1 ) comprising an aft section ( 8 ) formed from at least two half-shells ( 9 ) rotatably mounted such that they can each be deployed between a working position and a maintenance position under the action of a telescopic ram ( 11 ) and of a telescopic connecting rod ( 12 ) each respectively having a first end ( 13, 14 ) fastened in or on the jet engine and a second end ( 16, 17 ) fastened in the corresponding half-shell, characterized in that it comprises at least one damping member ( 19 ) arranged between each connecting rod and said half-shell, said damping member being designed such that it is in a prestressed state when the half-shell is in the working position.

TECHNICAL FIELD

The invention relates to a turbojet engine nacelle of an aircraft.

BACKGROUND

An aircraft is driven by a plurality of turbojet engines, each accommodated in a nacelle likewise housing an assembly of accessory actuating devices linked to its operation and ensuring various functions when the turbojet engine is in operation or at a standstill. These accessory actuating devices comprise, in particular, a mechanical system for the actuation of thrust reversers.

A nacelle generally has a tubular structure comprising an air inlet in front of the turbojet engine, a middle section intended for surrounding a blower of a turbojet engine, a rear section capable of housing thrust reversal means and intended for surrounding the combustion chamber of the turbojet engine, and generally terminates in an ejection nozzle, the outlet of which is located downstream of the turbojet engine.

Modern nacelles are often intended for housing a double-flow turbojet engine capable of generating, by means of the rotating blades of the blower, a stream of hot air (also called a primary stream) coming from the combustion chamber of the turbojet engine.

A nacelle generally has an external structure, called an outer fixed structure (OFS), which, with a concentric internal structure, called an inner fixed structure (IFS), comprising a cowl surrounding the actual turbojet engine structure at the rear of the blower, defines an annular flow channel, also called a flow section, intended for channeling a stream of cold air, called a secondary stream, which circulates outside the turbojet engine. The primary and secondary streams are ejected from the turbojet engine at the rear of the nacelle.

Each propulsive assembly of the aircraft is thus formed by a nacelle and a turbojet engine and is suspended on a fixed structure of the aircraft, for example under a wing or on the fuselage, by means of a pylori or mast attached to the turbojet engine or to the nacelle.

The rear section of the external structure of the nacelle is normally formed from two half-parts of substantially semi-cylindrical shape, on either side of a vertical longitudinal plane of symmetry of the nacelle, and mounted movably so as to be capable of being deployed between an operating position and a maintenance position for the purpose of giving access to the turbojet engine.

The two half-parts are generally mounted pivotably about a longitudinal axis forming a hinge in the upper part (at 12 o'clock) of the reverser. The half-parts are held in the closing position by means of locking bolts arranged along a junction line located in the lower part (at 6 o'clock).

Each half-part is opened with the aid of at least one jack and is kept open with the aid of at least one telescopic rod serving as a prop, said jack and said telescopic rod each having a first end generally fastened to the turbojet engine and a second end fastened in a front frame of said half-part, this front frame being the element making it possible to attach the rear section to a fixed part of the middle section of the nacelle.

In general terms, these half-parts are actuated by hydraulic or pneumatic jacks which require a network for the transport of fluid under pressure which is obtained either by the tapping of air or by extraction from a hydraulic circuit of the aircraft.

These systems necessitate considerable maintenance, are bulky and are intended to be replaced progressively by lighter and more reliable electrical actuating systems.

However, the electromechanical actuators likewise have some disadvantages which are to be overcome so as to be able to benefit fully from the advantages which they afford in terms of a saving of mass and of overall size.

With regard to the opening of the half-parts of a rear section, there is provision, for safety reasons, whereby an open half-part cannot be closed simply by the effect of gravity. It is therefore necessary to actuate the electrical jack in the corresponding direction in order to reclose the half-part. It is appropriate, however, to note that the power required for closing is, of course, less high than the power required for opening the half-parts.

A situation where damage frequently occurs is when an operator forgets to release the prop before triggering the jack for closing purposes. When such an omission happens, the electric motor is in a blocked situation.

Since the power for closing is lower than the maximum power of the jack, the power of the motor may rise in order to attempt to overcome the obstacle. The rod is then generally not sufficiently resistant and therefore risks breaking under the stress exerted by the electrical jack. On the other hand, it is still preferable for the prop to break, since, in the case of oversizing in order to prevent its fracture, the blocking of the electric motor of the jack risks causing the overheating of said motor and thus damaging its control electronics and/or its coils. Moreover, an oversizing of the prop would bring about an undesirable increase in mass.

Nevertheless, such an accident must be capable of being avoided.

BRIEF SUMMARY

The disclosure provides a turbojet engine nacelle comprising a front air inlet section, a middle section intended for surrounding a blower of the turbojet engine, and a rear section formed from at least two half-parts mounted movably in terms of rotation so as each to be capable of being deployed between an operating position and a maintenance position under the action of at least one jack and at least one telescopic rod capable of being locked in the deployed position, and each having respectively a first end fastened to the turbojet engine and a second end fastened in the corresponding half-part, characterized in that the jacks are associated with one or more actuating means equipped with at least one device limiting the active torque during a retraction phase of said jacks.

Thus, equipping the actuators with devices limiting the active torque during closing ensures that the torque exerted by the jacks will always be lower than the resistance of the rod. The rod therefore no longer risks breaking, the torque limiter disengaging the mechanism for actuating the jacks when the threshold value is overshot.

Advantageously, the actuating means are equipped with a device limiting the active torque during opening. The presence of a device limiting the active torque during opening makes it possible to limit the forces exerted on the half-part during its opening, these forces being capable of causing deformations in the half-part due to their highly localized nature.

Also advantageously, the device limiting the active torque during closing and the device limiting the active torque during opening are combined in a single double-acting device.

Preferably, the torque-limiting device possesses different calibration values for opening and closing.

According to a preferred embodiment of the invention, the jacks are jacks actuated by means of at least one electric motor.

Advantageously, the torque-limiting devices are mounted on a driveshaft of the electric motor.

Preferably, the torque-limiting device or torque-limiting devices comprises or comprise at least one ball-type torque-limiting device.

It is appropriate to note that the invention, although aimed more particularly at opening systems comprising electromechanical actuators, may also apply to pneumatic or hydraulic actuators.

The present invention also relates, on the one hand, to a propulsive assembly comprising a nacelle according to the invention arranged around a turbojet engine and, on the other hand, to an aircraft comprising at least one such propulsive assembly.

BRIEF DESCRIPTION OF THE DRAWING

The implementation of the invention will be understood more clearly from the detailed description given below, with reference to the accompanying drawing in which the single FIGURE is a diagrammatic illustration of a nacelle, seen from the front, having a rear section produced in the form of two half-parts shown in the opening position.

DETAILED DESCRIPTION

A nacelle 1, as illustrated in the single FIGURE, constitutes a tubular receptacle for a double-flow turbojet engine 5 and serves for channeling the airstreams which it generates by means of the blades of a blower (not illustrated), namely a stream of hot air passing through a combustion chamber of the turbojet engine and a stream of cold air circulating outside the turbojet engine.

The nacelle 1 is intended to be attached to a fixed structure of an aircraft, for example under a wing or in the region of the fuselage, by means of a mast 10.

The nacelle 1 possesses a structure comprising a front section 2 forming an air inlet, a middle section 3 surrounding the blower of the turbojet engine 5, and a rear section 4 surrounding the turbojet engine.

The rear section 4 comprises, on the one hand, an external structure 4 a generally incorporating a thrust reversal system and also forming an ejection nozzle and, on the other hand, an internal structure 4 b as the fairing of the turbojet engine 5, said internal structure defining with the external structure 4 a a flow section 7 intended for the circulation of the cold stream.

The external structure 4 a comprises a front frame 8 intended for making the connection between the external downstream structure 4 a and the middle part 2.

More specifically, the rear section 4 is produced in the form of two half-parts 9 surrounding the turbojet engine 5 and each articulated about a hinge line located in the vicinity of the mast 10, so as to be capable of changing alternately from an operating position, in which it is nearest to the turbojet engine and therefore closes the nacelle 1, to a maintenance position, in which it is deployed outward, as illustrated in the single FIGURE.

The opening and closing of the half-parts 9 takes place under the action of at least one jack 11 and of at least one telescopic rod 12, each having respectively a first end 13, 14 fastened in the turbojet engine and a second end 16, 17 fastened in a front frame 8 of the corresponding half-part 9.

The rod 12 is capable of being locked reversibly in the deployed position in which it then supports the corresponding half-part 9.

The jack 11 is a jack of the screw/ball type capable of being actuated by means of an electric motor (not shown).

This electric motor comprises an output shaft, on which a torque-limiting device is arranged according to the invention.

A torque limiter makes it possible to decouple a transmission when the transmission torque overshoots a certain predetermined value, called the calibration value. Such devices are known and are commercially available.

The limiter device installed will be active at least during a retraction movement of the jack 11 corresponding to the closing of a half-part 9.

Advantageously, a device limiting the active torque during opening may be provided.

The device limiting the active torque during opening may or may not be separate from the device limiting the active torque during closing. To be precise, there are double-acting torque limiters making it possible to fix different calibration values for each direction of rotation of the shaft of the electric motor.

By virtue of the invention, when the command for closing the half-parts 9 is engaged by an operator, if the latter has forgotten to release the rod 12 serving as a prop the torque-limiting device will make it possible to disengage the transmission when the half-part 9 comes into abutment against the rod 12. The fracture of the rod 12 is thus avoided.

Although the invention has been described in connection with particular exemplary embodiments, it is clear that it is no way limited to these and that it comprises all the technical equivalents of the means described, and also their combinations if these come within the scope of the invention. 

1. A turbojet engine nacelle comprising a front air inlet section, a middle section intended for surrounding a blower of the turbojet engine, and a rear section formed from at least two half-parts mounted movably in terms of rotation so as each to be capable of being deployed between an operating position and a maintenance position under action of at least one jack and of at least one telescopic rod capable of being locked in a deployed position, and each having respectively a first end fastened to the turbojet engine and a second end fastened in the corresponding half-part, wherein the jacks are associated with one or more actuating means equipped with at least one device limiting an active torque during a retraction phase of said jacks.
 2. The nacelle as claimed in claim 1, wherein the actuating means are equipped with a device limiting the active torque during opening.
 3. The nacelle as claimed in claim 2, wherein the device limiting the active torque during closing and the device limiting the active torque during opening are combined in a single double-acting device.
 4. The nacelle as claimed in claim 3, wherein the torque-limiting device possesses different calibration values for opening and closing.
 5. The nacelle as claimed in claim 1, wherein the jacks are jacks actuated by means of at least one electric motor.
 6. The nacelle as claimed in claim 6, wherein the torque-limiting device is mounted on a driveshaft of the electric motor.
 7. The nacelle as claimed in claim 1, wherein the torque-limiting device comprises at least one ball-type torque-limiting device.
 8. A propulsive assembly comprising a nacelle as claimed in claim 1 which is arranged around a turbojet engine.
 9. An aircraft comprising at least one propulsive assembly as claimed in claim
 8. 